There are many good reasons for reading the books of David James Duncan. His novel The River Why is as good a piece of fiction about fish, rivers, girls and the Meaning Of It All as you can ever hope to find, a genuinely funny, insightful and moving book that any sane reader will immediately forgive for its occasional forays into hippyishness. He is a serious fisherman and conservationist whose sterling work in helping to thwart mining companies in Montana is deftly chronicled in his latest offering, My Story As Told By Water. But this excellent book's most enjoyable essay, 'Fearless Leader', is not his own work at all. Instead, it is a reproduced letter from an old friend to whom he sent several spools of his favourite tippet material as a 50th birthday present – a gift which was returned, accompanied by this most acerbic and literate piece of correspondence.

I will leave you to discover the joys of this letter's contents for yourselves. Suffice to say that it highlights the extraordinary degree to which people disagree over something that is on the face of it one of the simpler elements of a flyfisher's armoury. As you are no doubt beginning to realise, there is almost no more bewildered fisherman anywhere on the planet than I, but if I were to highlight the one thing that baffles me more than any other the choice of tippet and leader material would be very close to the top of the list. By comparison, the Byzantine complexities of entomology and the physics of flycasting seem suddenly revealed as the simplest puzzles one will ever have to solve.

On the face of it, the problem is a simple one. How do I connect my flyline and leader to my fly in a way which will most effectively present said fly in a natural way? As soon as you start to think about this, the true extent of the problem becomes clear. Your leader must, always, be able to turn the fly over (I exclude users of shooting heads from this discussion, for reasons that are as much aesthetic as practical). But it must also be strong enough to survive the sudden shock imposed by a hooked fish or a wild strike. Depending on your point of view, it might have to stretch somewhat to absorb that shock (although as Duncan's friend points out, this is actually partly what the rod is for, and why it bends). And depending on where you're fishing, it must also be flexible enough to mimic the currents of a stream, or survive the pounding of a shallow-water wave, but stiff enough for you to keep control of the fly. It must be made of a material that will survive the crude knots that the average angler ties, and it must be resistant to abrasion. Sometimes it must sink on its own – but sometimes it must be made to sink a little with the aid of a variety of unguents and potions that again, people disagree wildly about. It must be invisible, or as near to it as makes a difference to a fish, in a variety of water and weather conditions. Choosing one kind of material to handle all these variables is about as easy as choosing one's last meal before public execution, and considerably less fun.

Countless manufacturers now sell spools of thin, pale stuff that they claim will catch us more fish. Ideally, they would like us to carry lots of spools around with us to handle all kinds of conditions and make them all kinds of profits – and for several years I have done just this, thus making a mockery of the idea that I need carry only one small bag around when out flyfishing. Yesterday, in an attempt to reduce the number of spools I routinely carry around with me to a number that I can carry comfortably in my trouser pocket, I went to three of London's most celebrated tackle shops with but one thought in my head; to buy a few spools of the material that, for whatever reason, I currently believe does the best general job for me under most conditions. It's made by Rio, it's called Fluoroflex and so far, I have had nothing but good things to say about it. And of course, none of them stock it – at least, not in any configuration that makes sense to an angler living on this particular island. If I had been fishing for tarpon in Florida, I would have been happily accomodated – the substance in question was available only in military-grade versions, thousands of yards or possibly miles of it, all so very relevant on Pall Mall. But trout fishing, sir? Not much call for that around here. And so I spent the next hour scratching my head, wishing that fishing's lowest common denominators were still horsehair and gut instead of co-polymer, fluorocarbon and nylon.

This is not the place for an exhaustive discussion of the merits of these materials. Apart from anything else, it would take me several years to even distinguish adequately between the brands, let alone discuss the various benefits of the materials themselves. (For what it's worth, I think co-polymer is too light and brittle, fluorocarbon too heavy and knot-intolerant, nylon monofilament too clumsy and visible, double-strength nylon too variable in its quality. Please send hatemail to the address below). By comparison, the choice of fly seems blindingly obvious, as self-evident as the choice of air or water as one's chosen breathing medium. And we have barely even started yet.

Let's assume we make a choice of some kind. How, now, to actually put it to use? Most of the anglers I know tie a small loop in the end of their tapered leader and tie lengths of their chosen tippet to that according to the number of flies and the depth at which they want to fish or the vagaries of the current across which they must cast. But I know one very good trout fisherman and AAPGAI casting instructor who eschews all of this, even the tapered leader, and simply ties 12 feet of level nylon monofilament to the end of his flyline with overhand loops; and I have seen him catch some very big and very difficult trout. Now let's turn to the Americans, for whom leader construction is an exercise in engineering and architecture as much as anything else; read everyone from Gierach to Grey and you will encounter descriptions of fine anglers 'building' leaders of impossible complexity as a matter of absolute course. There are now even some extraordinary spreadsheet tools to help you do this, based on Ritz's rule and line diameters and water temperature and Schweitzer lb-test formulae and concavity and convexity and much, much more.

How much does any of this matter? How many of us catch more fish, or fewer, because we make the wrong choices? The worst of all this is that I have absolutely no idea. I am happy with the rest of my life being chaotic and unpredictable, because someone will always helpfully tell me exactly where my behaviour is unacceptably shambolic and inappropriate. But trout can't talk, to the best of my knowledge (although some of them can sing, apparently) – and sometimes, I wish they could. It would be nice to hear, straight from the fishes' mouth, exactly which parts of this maze are actually worth navigating. In the meantime, I'd be happy for you to tell me what I should be doing on their behalf. Sometimes, we all need the help of a fearless leader.

Sean Geer (sean@fishmail.co.uk) is a freelance journalist
and author. He specialises in ritual humiliation by fish on four continents - most recently in
Ireland, where he became the first angler in history to not land a mayfly-caught trout on Lough
Corrib in the middle of the mayfly season. A retired seahorse conservationist and self-taught
zen origamist, he is currently writing a novel about sex, death and the meaning of fish.